Journal of Applied Physiology, Vol 65, Issue 4 1821-1826, Copyright © 1988 by American Physiological Society
Phosphate supplementation, cardiovascular function, and exercise performance in humans
D. L. Bredle, J. M. Stager, W. F. Brechue and M. O. Farber
Department of Physical Education, Indiana University, Bloomington 47405.
The use of oral phosphate (Pi) supplements to improve muscular work
performance has long been proposed without substantiating data. In a
double-blind, crossover experiment 11 male runners ingested calcium Pi (176
mmol/day) or placebo for 4 days. On the 3rd treatment day, subjects ran an
incremental maximal aerobic capacity test (VO2 max) on a treadmill, and on
the 4th day a treadmill run to exhaustion at approximately 70% VO2max. By
the 4th day of Pi loading, plasma Pi was significantly higher than control
(P less than 0.05); however, erythrocyte Pi, 2,3-diphosphoglycerate, and O2
half-saturation pressure of hemoglobin (P50) were not elevated. VO2 max was
not changed by the treatments (mean 62.9, 64.2, 64.9 ml.kg-1.min-1 for
control, Pi, and placebo bouts, respectively) nor was submaximal run time
to exhaustion (61.6 min for Pi, 65.5 min for placebo). Stroke volume at
steady-state VO2 was decreased with Pi (P less than 0.05), whereas cardiac
output tended (P = 0.07) to be lower. Greater arteriovenous O2 difference
(P less than 0.05) with Pi suggested a peripheral effect that increased O2
extraction. We concluded that in healthy individuals Pi loading produced no
improvement in work tolerance or aerobic capacity but did alter some
aspects of cardiovascular function.
